[GabrielF00]

The reason for the discrepancy is that Iron Dome was only activated for 27% of rockets fired. When it was activated, it was 90% accurate. Based on some the Wikipedia article is looks like they don't bother trying to intercept rockets that wouldn't land in populated areas. I don't know if that's for cost reasons or because targeting every rocket wouldn't be technically feasible or would degrade their capability or what.